In aeronautics, a balloon is an unpowered aerostat, which remains aloft or floats due to its buoyancy. A balloon may be free, moving with the wind, or tethered to a fixed point. It is distinct from an airship, which is a powered aerostat that can propel itself through the air in a controlled manner.

Many balloons have a basket, gondola or capsule suspended beneath the main envelope for carrying people or equipment (including cameras and telescopes, and flight-control mechanisms).

A balloon is conceptually the simplest of all flying machines. The balloon is a fabric envelope filled with a gas that is lighter than the surrounding atmosphere. As the entire balloon is less dense than its surroundings, it rises, taking along with it a basket, attached underneath, which carries passengers or payload. Although a balloon has no propulsion system, a degree of directional control is possible through making the balloon rise or sink in altitude to find favorable wind directions.

There are three main types of balloon:

The hot air balloon or Montgolfière obtains its buoyancy by heating the air inside the balloon; it has become the most common type.

other gases have included ammonia and methane, but these have poor lifting capacity and other safety defects and have never been widely used.[2]

The Rozière type has both heated and unheated lifting gases in separate gasbags. This type of balloon is sometimes used for long-distance record flights, such as the recent circumnavigations, but is not otherwise in use.

Both the hot air, or Montgolfière, balloon and the gas balloon are still in common use. Montgolfière balloons are relatively inexpensive, as they do not require high-grade materials for their envelopes, and they are popular for balloonist sport activity.

The first balloon which carried passengers used hot air to obtain buoyancy and was built by the brothers Josef and Etienne Montgolfier in Annonay, France in 1783: the first passenger flight was 19 September 1783, carrying a sheep, a duck, and a rooster.

The first tethered manned balloon flight was by a larger Montgolfier balloon, probably on 15 October 1783. The first free balloon flight was by the same Montgolfier balloon on 21 November 1783.

When heated, air expands, so a given volume of space contains less air. This makes it lighter and, if its lifting power is greater than the weight of the balloon containing it, it will lift the balloon upwards. A hot air balloon can only stay up while it has fuel for its burner, to keep the air hot enough.

The Montgolfiers' early hot air balloons used a solid-fuel brazier which proved less practical than the hydrogen balloons that had followed almost immediately, and hot air ballooning soon died out.

In the 1950s, the convenience and low cost of bottled gas burners led to a revival of hot air ballooning for sport and leisure.

The height or altitude of a hot air balloon is controlled by turning the burner up or down as needed, unlike a gas balloon where ballast weights are often carried so that they can be dropped if the balloon gets too low, and in order to land some lifting gas must be vented through a valve.

A man-carrying balloon using the light gas hydrogen for buoyancy was made by Professor Jacques Charles and flown less than a month after the Montgolfier flight, on 1 December 1783. Gas balloons have greater lift for a given volume, so they do not need to be so large, and they can also stay up for much longer than hot air, so gas balloons dominated ballooning for the next 200 years. In the 19th century, it was common to use town gas to fill balloons; this was not as light as pure hydrogen gas, having about half the lifting power, but it was much cheaper and readily available.

Light gas balloons are predominant in scientific applications, as they are capable of reaching much higher altitudes for much longer periods of time. They are generally filled with helium. Although hydrogen has more lifting power, it is explosive in an atmosphere rich in oxygen. With a few exceptions, scientific balloon missions are unmanned.

There are two types of light-gas balloons: zero-pressure and superpressure. Zero-pressure balloons are the traditional form of light-gas balloon. They are partially inflated with the light gas before launch, with the gas pressure the same both inside and outside the balloon. As the zero-pressure balloon rises, its gas expands to maintain the zero pressure difference, and the balloon's envelope swells.

At night, the gas in a zero-pressure balloon cools and contracts, causing the balloon to sink. A zero-pressure balloon can only maintain altitude by releasing gas when it goes too high, where the expanding gas can threaten to rupture the envelope, or releasing ballast when it sinks too low. Loss of gas and ballast limits the endurance of zero-pressure balloons to a few days.

A superpressure balloon, in contrast, has a tough and inelastic envelope that is filled with light gas to pressure higher than that of the external atmosphere, and then sealed. The superpressure balloon cannot change size greatly, and so maintains a generally constant volume. The superpressure balloon maintains an altitude of constant density in the atmosphere, and can maintain flight until gas leakage gradually brings it down.[3]

Superpressure balloons offer flight endurance of months, rather than days. In fact, in typical operation an Earth-based superpressure balloon mission is ended by a command from ground control to open the envelope, rather than by natural leakage of gas.

High-altitude balloons are used as high flying vessels to carry scientific instruments (like weather balloons), or reach near-space altitudes to take footage or photos of the earth. These balloons can fly over 100,000 feet (30.5 km) into the air, and are designed to burst at a set altitude where the parachute will deploy to safely carry the payload back to earth.[4]

Early hot air balloons could not stay up for very long because they used a lot of fuel, while early hydrogen balloons were difficult to take higher or lower as desired because the aeronaut could only vent the gas or drop off ballast a limited number of times. Pilâtre de Rozier realised that for a long-distance flight such as crossing the English Channel, the aeronaut would need to make use of the differing wind directions at different altitudes. It would be essential therefore to have good control of altitude while still able to stay up for a long time. He developed a combination balloon having two gas bags, the Rozier balloon. The upper one held hydrogen and provided most of the steady lift. The lower one held hot air and could be quickly heated or cooled to provide the varying lift for good altitude control.

In 1785 Pilâtre de Rozier took off in an attempt to fly across the Channel, but shortly into the flight the hydrogen gas bag caught fire and de Rozier did not survive the ensuing accident. This earned de Rozier the title "The First to Fly and the First to Die".

It wasn't until the 1980s that technology was developed to allow safe operation of the Rozier type, for example by using non-flammable helium as the lifting gas, and several designs have successfully undertaken long-distance flights.

A tethered helium balloon gives the public rides to 500 feet (150 m) above the city of Bristol, England. The inset shows detail of the gondola.

As an alternative to free flight, a balloon may be tethered to allow reliable take off and landing at the same location. Some of the earliest balloon flights were tethered for safety, and since then balloons have been tethered for many purposes, including military observation and aerial barrage, meteorological and commercial uses.

The natural spherical shape of a balloon is unstable in high winds. Tethered balloons for use in windy conditions are often stabilised by aerodynamic shaping and connecting to the tether by a halter arrangement. These are called kite balloons.

A kite balloon is distinct from a kytoon, which obtains a portion of its lift aerodynamically.

Unmanned hot air balloons are popular in Chinese history. Zhuge Liang of the Shu Han kingdom, in the Three Kingdoms era (220–280 AD) used airborne lanterns for military signaling. These lanterns are known as Kongming lanterns (孔明灯).[5][6] Mongolian army studied Kongming lanterns from Chinese and used it in Battle of Legnica during Mongol invasion of Poland.[7] This is the first time balloon was known by western world. In 1709 the Portuguese cleric Bartolomeu de Gusmão made a balloon filled with heated air rise inside a room in Lisbon. He is also claimed to have built a balloon named Passarola (Big bird) and attempted to lift himself from Saint George Castle in Lisbon, landing about one kilometre away.[8][9][10][11][12][13][citation needed] This claim is not generally recognized by aviation historians outside the Portuguese speaking community, in particular the FAI.[14][15]

The first Italian balloon ascent was made by Count Paolo Andreani and two other passengers in a balloon designed and constructed by the three Gerli brothers, on 25 February 1784. A public demonstration occurred in Brugherio a few days later, on March 13, 1784, when the vehicle flew to a height of 1,537 metres (5,043 ft) and a distance of 8 kilometres (5.0 mi).[17] On March 28 Andreani received a standing ovation at La Scala, and later a medal from Joseph II, Holy Roman Emperor.

De Rozier, together with Joseph Proust, took part in a further flight on 23 June 1784, in a modified version of the Montgolfiers' first balloon christened La Marie-Antoinette after the Queen. They took off in front of the King of France and King Gustav III of Sweden. The balloon flew north at an altitude of approximately 3,000 metres, above the clouds, travelling 52 km in 45 minutes before cold and turbulence forced them to descend past Luzarches, between Coye et Orry-la-Ville, near the Chantilly forest.

The first aircraft disaster occurred in May 1785 when the town of Tullamore, County Offaly, Ireland was seriously damaged when the crash of a balloon resulted in a fire that burned down about 100 houses, making the town home to the world's first aviation disaster. To this day, the town shield depicts a phoenix rising from the ashes.

The earliest successful balloon flight recorded in Australia was by William Dean in 1858. His balloon was gas-filled and travelled 30 km with two people aboard.[20]

Henri Giffard also developed a tethered balloon for passengers in 1878 in the Tuileries Garden in Paris. The first tethered balloon in modern times was made in France at Chantilly Castle in 1994 by Aerophile SA.

The first military use of a balloon was at the Battle of Fleurus in 1794, when L'Entreprenant was used by the French Aerostatic Corps to watch the movements of the enemy. On 2 April 1794, an aeronauts corps was created in the French army; however, given the logistical problems linked with the production of hydrogen on the battlefield (it required constructing ovens and pouring water on white-hot iron), the corps was disbanded in 1799.

Hydrogen-filled balloons were widely used during World War I (1914–1918) to detect enemy troop movements and to direct artillery fire. Observers phoned their reports to officers on the ground who then relayed the information to those who needed it. Balloons were frequently targets of opposing aircraft. Planes assigned to attack enemy balloons were often equipped with incendiary bullets, for the purpose of igniting the hydrogen.

The Aeronaut Badge was established by the United States Army in World War I to denote service members who were qualified balloon pilots. Observation balloons were retained well after the Great War, being used in the Russo-Finnish Wars, the Winter War of 1939–40, and the Continuation War of 1941–45.

Large helium balloons are used by the South Korean government and private activists advocating freedom in North Korea. They float hundreds of kilometers across the border carrying news from the outside world, illegal radios, foreign currency and gifts of personal hygiene supplies. A North Korean military official has described it as "psychological warfare" and threatened to attack South Korea if their release continued.[22][23]

Ed Yost redesigned the hot air balloon in the late 1950s using rip-stop nylon fabrics and high-powered propane burners to create the modern hot air balloon. His first flight of such a balloon, lasting 25 minutes and covering 3 miles (5 km), occurred on 22 October 1960 in Bruning, Nebraska. Yost's improved design for hot air balloons triggered the modern sport balloon movement. Today, hot air balloons are much more common than gas balloons.

A balloon in space uses internal gas pressure only to maintain its shape.

The Echo satellite was a balloon satellite launched into Earth orbit in 1960 and used for passive relay of radio communication. PAGEOS was launched in 1966 for worldwide satellite triangulation, allowing for greater precision in the calculation of different locations on the planet's surface.

On 19 October 1910, Alan Hawley and Augustus Post landed in the wilderness of Quebec, Canada after traveling for 48 hours and 1887.6 kilometers (1,173 mi) from St. Louis during the Gordon Bennett International Balloon Race, setting a distance record that held for more than 20 years. It took the men a week to hike out of the woods, during which time search parties had been mobilized and many had taken the pair for dead. [27]

On 13 December 1913 through 17 December 1913 Hugo Kaulen stayed aloft for 87 hours. His record lasted until 1976. [28]

Ben Abruzzo was the first man to cross the Pacific Ocean in a hot air balloon.

On 31 August 1933, Alexander Dahl took the first picture of the Earth's curvature in an open hydrogen gas balloon.

The helium-filled Explorer II balloon, piloted by US Army Air Corps officers Capt. Orvil A. Anderson, Maj. William E. Kepner and Capt. Albert W. Stevens, reached a new record height of 22,066 m (72,395 ft) on 11 November 1935. This followed the same crew's previous near-fatal plunge in July 1934 in a predecessor craft, Explorer, after its canopy ruptured just 190 m (624 ft) short (it transpired) of the then-current altitude record of 22,000 m (72,178 ft) set by the Soviet balloon Osoaviakhim-1.

In 1976, Ed Yost set 13 aviation world’s records for distance traveled and amount of time aloft in his attempt to cross the Atlantic Ocean —solo— by balloon (3.938 km, 107:37 h).

The altitude record for an unmanned balloon is 53.0 kilometres (173,882 ft), reached with a volume of 60,000 cubic metres. The balloon was launched by JAXA on 25 May 2002 from Iwate Prefecture, Japan.[31] This is the greatest height ever obtained by an atmospheric vehicle. Only rockets, rocket planes, and ballistic projectiles have flown higher.

In 2015, the two pilots Leonid Tiukhtyaev and Troy Bradley arrived safely in Baja California, Mexico after a journey of 11,265 km. The two men, originally from Russia and the United States of America respectively, started in Japan and flew with a helium balloon over the Pacific. In 160 hours, the balloon named "Two Eagles" arrived in Mexico, which is a new long-distance record for a gas balloon.[32]

^ abcThe 4 May 1961 FAI Absolute Altitude (#2325) record for balloon flight set by Malcolm Ross and Victor Prather is still current, as it requires the balloonist to descend with the balloon. The succeeding altitude records were set by parachutists who either separated from or abandoned the balloon at the flight ceiling.[30]

^ ab"FAI Ballooning Commission Achievements". Fédération Aéronautique Internationale. Retrieved 2010-04-11. A list of notable balloon and airship flights has been assembled by Hans Åkerstedt from Sweden. The list has been compiled with much help from Troy Bradley, USA and Norman Pritchard, UK. Information from many other sources have also been used – FAI record files, personal log books and commercially available literature.

Note 1: A tiltwing or tiltrotor aircraft functions as an aeroplane during normal (horizontal) flight and as a helicopter during low-speed flight.

Note 2: For full-size aircraft with powered rotors the rotor is normally tilted to achieve thrust (e.g. in a helicopter). Some toys (e.g. balloon helicopter) do have a powered rotor with no means to tilt the rotor to produce horizontal thrust.